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Date: Sun, 24 Oct 2010 08:04:31 +0200
From: Jens Axboe <jaxboe@...ionio.com>
To: Eric Dumazet <eric.dumazet@...il.com>
CC: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] disk_free_ptbl_rcu_cb() crash
On 2010-10-23 23:10, Eric Dumazet wrote:
> Current Linus tree makes my machine crash in disk_free_ptbl_rcu_cb(),
> while booting...
>
> commit 7681bfeeccff5ef seems the problem ?
>
> Following patch solves the NULL dereference, but this is only to show
> you where the problem is, not a real fix, of course.
Darn. Your fix is on the right path, you missed one though. I think it's
cleaner to move this into the elevator helpers, so that the callers can
remain clean.
Can you verify that this works too?
diff --git a/block/elevator.c b/block/elevator.c
index 2569512..f08ae2d 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -590,11 +590,8 @@ void elv_drain_elevator(struct request_queue *q)
/*
* Call with queue lock held, interrupts disabled
*/
-void elv_quiesce_start(struct request_queue *q)
+void __elv_quiesce_start(struct request_queue *q)
{
- if (!q->elevator)
- return;
-
queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
/*
@@ -610,11 +607,31 @@ void elv_quiesce_start(struct request_queue *q)
}
}
-void elv_quiesce_end(struct request_queue *q)
+void elv_quiesce_start(struct request_queue *q)
+{
+ if (q->elevator) {
+ spin_lock_irq(q->queue_lock);
+ __elv_quiesce_start(q);
+ spin_unlock_irq(q->queue_lock);
+ }
+}
+
+void __elv_quiesce_end(struct request_queue *q)
{
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
}
+void elv_quiesce_end(struct request_queue *q)
+{
+ if (q->elevator) {
+ unsigned long flags;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ __elv_quiesce_end(q);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+ }
+}
+
void elv_insert(struct request_queue *q, struct request *rq, int where)
{
int unplug_it = 1;
@@ -969,7 +986,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
* Turn on BYPASS and drain all requests w/ elevator private data
*/
spin_lock_irq(q->queue_lock);
- elv_quiesce_start(q);
+ __elv_quiesce_start(q);
/*
* Remember old elevator.
@@ -995,9 +1012,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
* finally exit old elevator and turn off BYPASS.
*/
elevator_exit(old_elevator);
- spin_lock_irq(q->queue_lock);
elv_quiesce_end(q);
- spin_unlock_irq(q->queue_lock);
blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
diff --git a/block/genhd.c b/block/genhd.c
index a8adf96..7d4d860 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -930,14 +930,9 @@ static void disk_free_ptbl_rcu_cb(struct rcu_head *head)
struct disk_part_tbl *ptbl =
container_of(head, struct disk_part_tbl, rcu_head);
struct gendisk *disk = ptbl->disk;
- struct request_queue *q = disk->queue;
- unsigned long flags;
kfree(ptbl);
-
- spin_lock_irqsave(q->queue_lock, flags);
- elv_quiesce_end(q);
- spin_unlock_irqrestore(q->queue_lock, flags);
+ elv_quiesce_end(disk->queue);
}
/**
@@ -962,10 +957,7 @@ static void disk_replace_part_tbl(struct gendisk *disk,
if (old_ptbl) {
rcu_assign_pointer(old_ptbl->last_lookup, NULL);
- spin_lock_irq(q->queue_lock);
elv_quiesce_start(q);
- spin_unlock_irq(q->queue_lock);
-
call_rcu(&old_ptbl->rcu_head, disk_free_ptbl_rcu_cb);
}
}
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index b81bfc0..cf4d1ee 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -367,16 +367,13 @@ static void delete_partition_rcu_cb(struct rcu_head *head)
struct hd_struct *part = container_of(head, struct hd_struct, rcu_head);
struct gendisk *disk = part_to_disk(part);
struct request_queue *q = disk->queue;
- unsigned long flags;
part->start_sect = 0;
part->nr_sects = 0;
part_stat_set_all(part, 0);
put_device(part_to_dev(part));
- spin_lock_irqsave(q->queue_lock, flags);
elv_quiesce_end(q);
- spin_unlock_irqrestore(q->queue_lock, flags);
}
void delete_partition(struct gendisk *disk, int partno)
@@ -398,9 +395,7 @@ void delete_partition(struct gendisk *disk, int partno)
kobject_put(part->holder_dir);
device_del(part_to_dev(part));
- spin_lock_irq(q->queue_lock);
elv_quiesce_start(q);
- spin_unlock_irq(q->queue_lock);
call_rcu(&part->rcu_head, delete_partition_rcu_cb);
}
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 80a0ece..2d30300 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -122,7 +122,9 @@ extern void elv_completed_request(struct request_queue *, struct request *);
extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
extern void elv_put_request(struct request_queue *, struct request *);
extern void elv_drain_elevator(struct request_queue *);
+extern void __elv_quiesce_start(struct request_queue *);
extern void elv_quiesce_start(struct request_queue *);
+extern void __elv_quiesce_end(struct request_queue *);
extern void elv_quiesce_end(struct request_queue *);
/*
--
Jens Axboe
--
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